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Phosphorus, Serum / Plasma

Item Value
Approval req'd? No
Available Stat? Yes
Test code PO4
Test group Phosphorus
Performed by Parnassus & Mt. Zion Chemistry
In House Availability Test available 24 hours per day 7 days per week
Method Spectrophotometric (molybdate)
Container type Gold top or Light Green top
Amount to Collect 1 mL blood Click here for Microdetermination info
Sample type Serum or plasma
Preferred volume 0.5 mL serum or plasma
Min. Volume 0.2 mL serum or plasma Click here for Microdetermination info
Units mg/dL
Normal range
< 1 month 3.9-7.7 mg/dL
1 month - 11 months 3.5-6.6 mg/dL
1 year - 3 years 3.1-6.0 mg/dL
4 years - 12 years 3.0-5.7 mg/dL
13 years - 15 years 2.9-5.1 mg/dL
≥ 16 years 2.6-4.9 mg/dL


1. Normal range for pediatric patients adapted from Soldin, Steven J., "Pediatric Reference Ranges", 6th edition, AACC Press, 2007, method 1.
2. Normal range for adults was determined by testing 271 male and female healthy blood donors at UCSF.

Critical value < 1.0 mg/dL
Synonyms PO4
Stability Room temperature 8 hours, refrigerated 2 days, frozen at -20C 1 week
Turn around times STAT 1 hour, Routine: 4 hour
Additional information To convert mg/dL to mmol/L (SI units) multiply by 0.323.

Phosphorus, like potassium, is released by platelets during clotting, and serum levels are approx. 0.2 mg/dL higher than those measured in plasma. Levels can be falsely elevated by thrombocytosis, though not as predictably as those for potassium.

High dose liposomal amphotericin B treatment may also cause falsely elevated serum phosphorus values in this DXC assay (see Bailey H and Chan E, Clin Chem 53:795-6, 2007)
CPT coding 84100
LOINC code 2777-1
Last Updated 10/15/2014 11:48:46 AM
Entry Number 740
Lab Procedure Link Click here for Procedure
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